Hydraulics Flashcards
How many hydraulic systems are on the airplane?
3 Independent systems: HYD 1, HYD 2, and HYD 3
What systems use hydraulic power?
Flight controls, Spoilers, Landing gear, Nose wheel steering, Wheel brakes, Thrust reversers
Can hydraulic fluid be transferred between each system?
No
How many hydraulic pumps are on the airplane?
7 total: 2 EDPs (Engine Driven Pumps), 4 ACMPs (AC Motor Pumps), 1 PTU
What are the basic components of the hydraulic systems?
Reservoir, Pumps, Accumulator
What is the purpose of the accumulator?
Helps to maintain constant pressure by covering transient demands and helps to avoid pump cavitation
When will ACMP 1 or 2 automatically activate?
Ground: Flaps > 0, and TL set to TOGA, OR Grounds > 50 kts (Remains on for 60 seconds after TL at TOGA);
Flight: Engine failure or EDP failure, OR Flaps > 0 (Remains on for 60 seconds after landing)
What are some important items controlled by HYD 2 system?
Landing gear, Nose wheel steering, Inboard brakes
What is the PTU?
Power Transfer Unit: Mechanical pump that uses HYD 1 power to provide HYD 2 pressure
What is the primary purpose of the PTU?
To allow landing gear retraction and extension in the event of an engine 2 or EDP 2 failure
When will the PTU automatically activate?
During takeoff and landing with flaps > 0, if Engine 2 fails, or EDP 2 fails.
(Must have above 12% quantity in #2 Hydraulic Reservoir and Airplane is Airborne. Engine #1 EDP must be operational.)
How is single engine taxi possible if nose wheel steering is on HYD 2?
Releasing the parking brake activates ACMP 2
What is the primary purpose of HYD 3 system?
Back-up for the Flight controls
Why does HYD ACMP 3A pump switch have an ON position and HYD ACMP 3B have an AUTO position?
HYD ACMP 3A pump is primary and has no automation; HYD ACMP 3B pump is a back-up and automatically activates if ACMP 3A fails with normal AC power
What, if any, HYD ACMP will function if the RAT is the only power source?
HYD ACMP 3A only with no backup
In an electrical emergency what provides hydraulic pressure to flight controls until the RAT comes online?
HYD 3 accumulator (After 8 seconds the RAT will power ACMP 3A)
In an electrical emergency can HYD 3 system power requirements overload the RAT?
No. A flow limiter valve and a pump unloader valve are used to reduce flow and limits pump electrical power draw to prevent a RAT stall
